1. Field of the Invention
The present invention relates to an air classifier method and apparatus in order to separate solids by air classification while eliminating emissions. More specifically, this invention is directed to an air classifier system which eliminates emissions, provides a substantially closed circulating system, and eliminates the need for bleed off of air in the system.
2. Prior Art
Air classifier systems have been in use for a number of years and are used in various applications. In one known application, materials to be separated and classified come from the result of shredding of waste materials, such as cars or vehicle parts. The cars or other materials are initially put through a shredder which pulls apart the materials. They may also separate the materials, such as with magnets so that metal materials are pulled off. In other cases, a trommel device may be used so that materials under a certain size will be separated.
The resulting material or materials are then used as an in-feed product on an in-feed conveyer to an air classifier separating system. Materials that are heavier than the force of the air driven by the fan drop by gravity into a large fraction discharge chute. Materials that are lighter than the force of air driven by the fan, sometimes referred to as “fluf” are driven up through a light fraction discharge chute and gathered in a hopper.
The air classifier system is a continuous flow system with forced air from the lighter fraction discharge passed back toward the air fan so that the system operates in continuous fashion. Although a hanging curtain or other mechanism is used at the in-feed conveyor, the force of air through the system will draw a portion of air in from the atmosphere.
If this incoming air is not vented, the efficiency of the system is reduced and/or airflow will escape somewhere from the system.
Accordingly, many existing air classifier systems include a bleed-off duct or bleed-off exhaust. A certain amount of air in the system is bled off through a duct into the atmosphere. The bleed-off duct may include a manual damper to adjust the rate of flow. This bleed-off fraction may be up to 10%–20% of the total airflow through the system depending upon the amount of air leaking in the system.
A significant problem with conventional bleed-off exhaust is that the fluid from the bleed-off is dust and dirt-laden, which when exhausting through a discharge stack, results in unwanted emission. The amount of dust being emitted may be in excess of allowable emission levels and an air permit may be required to operate the system. Another problem with conventional bleed-off exhaust is that due to excessive emissions, the past remedies have been to add secondary collection devices such as filters or wet scrubbers, all of which are costly to purchase, maintain and operate. Another problem with conventional bleed-off exhausts is that due to many stringent air permitting issues, many people will not consider the main air classifier as a viable process for their location, which results in either an inferior process, or inferior finished product, or no process at all.
While existing devices may be suitable for the particular purpose to which they address, they are not as suitable for eliminating the need for a bleed-off stack from an air classifying cleaning system, and thus eliminating air pollution or the need for a permit to operate an air emission source.
It is a further object and purpose of the present invention to provide an air classifier to separate solids which eliminates the normal need for a bleed-off stack or duct, eliminating the air pollution generated.
It is a further object and purpose of the present invention to provide an air classifier having an emission source eliminator.
It is a further object and purpose of the present invention to provide an air classifier to separate solids which results in a closed fluid system.
Another object and purpose of the present invention is to provide an air classifier to separate solids which decreases the need to obtain governmentally issued emission permits.
A further object and purpose of the present invention is to provide an improved air classifier system that may retrofit to existing systems or incorporated in new systems.